Numerical Simulation Study Of Dilute Phase Pneumatic Conveying In Shrimp Automatic Feeding System

In accordance with the actual layout of the industrial production site as well as the fundamental production requirements of the practical offshore shrimp cultivation project,an automated pneumatic feeding system has been designed with a length of more than 300 M,supplying a total of 48 shrimp ponds and satisfying the feeding demands of both adult and juvenile shrimps based on dilute phase pneumatic conveying.In order to comprehensively study the theoretical system of pneumatic conveying of shrimp feed pellets,a combination of theoretical analysis,experimental study and numerical simulation was used to investigate the pressure drop characteristics,energy consumption and particle motion characteristics of the system.Experimental measurements of the fundamental properties of shrimp feed pellets as well as the stacking and collapse angles were performed and their flow characteristics were comprehensively evaluated.The experimentally measured physical parameters were applied to the modelling of shrimp feed pellets and pipes.Simultaneously,a CFD-DEM model was developed to simulate a dilute phase pneumatic conveying pipeline for an automatic shrimp feed feeding system,and the accuracy of the model was successfully validated through experimental verification on a test setup.The pressure drop characteristics and system energy consumption of automatic feeding systems have been thoroughly investigated.The variation of pressure drop characteristics and system energy consumption in long vertical and long horizontal ducts is investigated.The variation of unit pressure drop with inlet air velocity and solid loading velocity is thoroughly analysed,and the pressure loss of the two types of ducts is also analysed in accordance with the additional pressure drop theory.The investigation results have revealed that in long vertical pipes,the unit pressure drop continuously increases as the solid loading velocity increases.At the same time,the unit pressure will decrease initially before increasing as the inlet wind velocity increases.In long horizontal ducts,the unit pressure drop consistently increases with increasing solid loading speed and inlet wind speed.Therefore,the optimum solid-to-gas ratio that minimises the energy consumption of the system at different solid loading rates has been successfully determined.The movement characteristics of pellets in an automated pneumatic feeding system have been comprehensively examined.An analytical examination of the movement of shrimp feed pellets at the microscopic level in conjunction with an analysis of the forces on the pellets in the pipe was undertaken with the objective of being able to explain the variation in the pressure drop characteristics of the pellets in this pneumatic conveying system.The results evidently revealed that the shrimp feed particles flowed in a uniform state of suspension in the long vertical pipe and partially deposited with a partially suspended state in the horizontal pipe.The range of flow state transitions within the two pipes has been identified by the particle population suspension velocity.Concurrently,a comparison of the front-end bends of the vertical and horizontal ducts revealed that the movement of particles within the bends had a considerable effect on the long straight ducts.For the vertical duct,the unit pressure drop is at the minimum point at an inlet air velocity of 24m/s.It was found that this inlet air velocity is the fastest inlet air velocity for the particles in the long straight pipe to enter the suspended flow state,and it is also the cut-off point for the change of particle distribution state at the exit section of the elbow at the front end of the vertical pipe.